Structural basis of meiotic chromosome synaptic elongation through hierarchical fibrous assembly of SYCE2-TEX12

James Dunce, Lucy Salmon, Owen Richard Davies*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The synaptonemal complex (SC) is a supramolecular protein assembly that mediates synapsis between homologous chromosomes during meiosis. SC elongation along the chromosome length (up to 24μm) depends on its midline α-fibrous component SYCE2-TEX12. Here, we report X-ray crystal structures of human SYCE2-TEX12 as an individual building-block and upon assembly within a fibrous lattice. We combine these structures with mutagenesis, biophysics and electron microscopy to reveal the hierarchical mechanism of SYCE2-TEX12 fibre assembly. SYCE2-TEX12’s building-blocks are 2:2 coiled-coils which dimerise into 4:4 hetero-oligomers and interact end-to-end and laterally to form 10-nm fibres, which intertwine within 40-nm bundled micrometre-long fibres that define the SC’s midline structure. This assembly mechanism bears striking resemblance with intermediate filament proteins vimentin, lamin and keratin. Thus, SYCE2-TEX12 exhibits behaviour typical of cytoskeletal proteins to provide an α-fibrous SC backbone that structurally underpins synaptic elongation along meiotic chromosomes.
Original languageEnglish
Pages (from-to)681–693
Number of pages13
JournalNature Structural & Molecular Biology
Volume28
DOIs
Publication statusPublished - 9 Aug 2021

Keywords

  • meiosis
  • chromosome structure
  • double-strand break
  • chiasmata
  • synaptonemal complex
  • SYCE2
  • TEX12
  • self-assembly
  • coiled-coil
  • small-angle X-ray scattering
  • biophysics
  • X-ray crystallography
  • intermediate filaments

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